Advice sought on rust removal and repainting dome struts

[watsonic]

Hi all,

I have a five year old 2v dome I built out of EMT (steel conduit). Over the years the paint has come off the tips and I've started to see rust building up, especially in the holes that were drilled out as well as the very ends of the struts.

I'm looking for advice on the best procedure to remove that rust and get the tips repainted so this thing will last another 5 or 10 years.

Here's what I have so far. Please jump in with any comments, even if speculative...

1. Remove as much rust and old flaking paint as possible via physical means. Namely sanding.
[worry 1: I can't get the rust out of the cracks at some the ends or where one edge obstructs another (in some of the holes)]
[worry 2: do I risk taking off some of the rust resistant protective coating which came with the EMT?]

2. Apply self-etching primer as suggested here: http://wiki.answers.com/Q/How_do_you_re ... urity_door and detailed here: http://carpaint.blogspot.com/2006/07/se ... rimer.html

3. Sand down lightly to smooth out in prep for paint. [maybe this step isn't necessary?]

4. Apply paint. I was thinking maybe paint in a container I can dip the ends into. That way it will coat all those hard to reach surfaces and cracks. And also avoids aerosols. [what sort of paint will work best here? whats going to best resist the strut on strut abrasion (like the last paint wasn't able to)?]

Cheers,
watson

[Captain Goddammit]

I think I'd use a sandblaster. It'll get the hard to reach areas, and it's SO much easier. If you haven't got one, you'll be surprised at how cheap they are! Of course, you'll also need a compressor, but you can rent one if you haven't already got one.

I don't think any paint is going to resist the metal-on-metal abrasion, but periodic maintenance like you are doing should keep it alive.

[watsonic]

I certainly don't have these tools but I might know some friends around town who do. This is a great suggestion. Thanks!

As to the type of paint, I still feel like some paints must be superior to others in this respect. Like you say, I don't imagine any paint can completely survive the abrasion...

Cheers,
watson

[zabsinth]

Since this is a long-term investment, you might want to call around to different powdercoating shops in your area - they'll blast 'em and put a very sturdy finish on. I've heard that bike frames start around $100, so this could cost a decent amount, but it will last FOREVER.

[robotland]

You can clean rust from your strut ends by grinding them around in a bucket of dry sand or, better yet, coarse sandblasting grit like the black "clinker stuff". A wire brush paint stripper on a drill does wonders too.

[Toolmaker]

Goto Sears and buy a drill.. corded probably more sensible choice. Also purchase a wire wheel for the drill. After your done.. return the drill. This also saves money for the next person thats willing to buy used for a discount.

PS Electrolytic "De-Rusting" info is available if need be but that is a pain in the ass to bother with for dome struts. I would do the wire wheel.. will probably be trhe fastest quick and dirty and cheap way to go. You may want to run through the holes again to clean the inside out but thats prolly overkill this late in the game.

[gyre]

Absolutely do not take off the old paint if it is on solid.
Roughen up the surface enough for adherence.
This is why I don't like conduit over proper galvanized pipe or solid aluminum tubing.

If you use blasting, I would use something relatively soft like shells.
You can use a wire brush of 3 types in a dremel for tight spots but you can't reach everything.
You can shape your own tips in some materials for tight spots.

Good stiff hand held brushes are what you want, expensive and hard to find.
Worth it too. I use fuller.
A wire wheel on a grinder or other stand is best in general.
You need a stiff one for scraping rather than polishing.
They can be expensive, but last forever.
Try not to polish the clean metal or the plating if you wish to paint.

Etching primer may be a good choice.
It's a good idea to test.
Cold galvanizing zinc is what some recommend.
I mostly use oil based rustoleum zinc oxide primer or fish oil primer for heavy rust.
They have a 3 stage anti rust system too.
Usually I use HD Aluminum over the top.
This leafs and you must keep stirring it as you paint.
You can put it on with a brush though.
It takes a long time to dry.
So do the primers if they are thick.
You should wait for them to dry.
Full cure can take a month for each coat.

There are some jazzy finishes for rust on old cars in hemmings.
I hear good things but they aren't cheap.

You might want to dip the ends in liquid plastic for tools or something similar.

I have used the water based rustoleum zinc primer and I think it's an etching type.
The finish is exceedingly tough.
I really hate using the stuff though.
Wear eye protection and gloves.
That may suit you.

You could use heatshrink material over the ends for protection and even color coding.
The best is irradiated pvc only in black.
They range up to teflon, with varied costs.

You can get your own phosphate wash.
I do that myself.
This does etching.

Some steels nothing will be good enough.
Use aluminum or 316L or get better galvanized plating to start with.

You can get kits to powder coat your own stuff in an oven or with infrared lamps.
All powder coating is not the same.

[gyre]

Personally I would brush all the rust off and grease or dip OR
sand carefully the bad spots and paint or dip or put shrink on.
(Just sanding the worst spots so paint will grip. You could phospate after that and wash)

[EspressoDude]

use naval jelly/phosphoric acid to remove rust

rinse

dry

rinse

dry

use SEM self etching primer $12.00 rattle can or quarts for dipping. use ventilation

using SEM increases paint bonding by a huge amount well worth the time

do this as a winter project, not NOW!!!

[gyre]

Is naval jelly a good choice on conduit?
I have used some similar things with poor results, but I think it may have been the material.
I gave one to someone else and they loved it.

I'm not familiar with SEM.
Is it worth the cost in this application over rustoleum industrial?
(By the way, you used to have to go to an industrial supply for the industrial paints, but some show up in hardware stores now. Cheaper in a supply house for me.)

There is always a better product, but usually there is a break point in price.

For clear coat, I recommend clear silicone conformal coating made for electronics.
Very tough.
I use the aerosols.
I've never had the nerve to price it past a pint in cans.

[watsonic]

ah lots of good advice here.

i'm feeling a bit of information overload from all the suggestions.

maybe thats a good thing and means there are several good ways to do this.

does anyone have experience with the product Rustoleum Rust Reformer? apparently its pretty decent at stopping the process of rusting and transforming rust into something else (black) which can be easily painted over. (from anecdotes and this epinions article ... look halfway down in the review to see talk of rust reformer: http://www.epinions.com/content_110379830916)

one question in my mind is whether i would want to use a self etching primer *in addition* to that product or not.

so far the ideal process to me sounds like:

1. sandblast if i can find that equipment. and/or use my drill with a really tough wirebrush which would do well in the drilled out holes (tho clearly this still can't fit into the small cracks on the tips).

2. apply rustoleum rust reformer to places where rust still shows.

3. [maybe] apply a self etching primer. to regalvanize and prime.

4. sand down enough to make sure theres a nice surface to paint on.

5. paint with some sort of appropriate paint [which i still haven't pinpointed yet! help!].

cheers,
watson

[gyre]

A friend suggest muriatic acid in a weak solution, which must then be carefully neutralized.
He also suggests a stainless steel brush always.
Do not use anything but a rag in paint thinner to clean dust.
Normal paint products can leave residue.


I think you should consider maintenance.
In some cases a simple but easy to repeat approach is best.
You could clean the rust off and phosphoric dip and cold galvanize by dipping and done or add plastic dip.
Sleeves could be made from inner tubes or hose + the heat shrink I mentioned.
He suggests washers possibly of rubber to avoid scratches.
Also plates on both sides if not in use now.

You may want to use a simple if not ideal approach so it will be easy next time.

Many would clean and use the cold galvanizing and stop.
Same option is possible at any other step.

If you are adding another coat, only enough sanding is needed to break old surfaces and cause grip.
I use a heavy grade and use it very lightly- Very.

There is an oil made just for the inside of tubes of this type.
Another option, though intended for use before closing the ends.

My friend thinks the naval jelly is not a good approach for this due to the mess, not that it won't work.

I'm not familiar with the product reformer.
Some of these only work on rust and grip poorly on smooth surfaces.

I suggest you experiment a bit.

Also, rustoleum has a primer made for medium high temperature uses that cures without baking, unique as far as I know.
Great in places that are subject to heat but not enough for high temperature paint.
X-60 350 F.

Is maintenance or appearance the primary issue here?

[EspressoDude]

Use muriatic or phosphoric acid to neutralize/remove rust. The rustoleum product is one of these.

Definately use SEM self etching primer. I won't paint metal without it, even considering the cost.

Do not sand the SEM, the etch is only a few molecules deep.

This sounds like a lot of work considering the cost of EMT.

[gyre]

The primer layer would be thicker than that, wouldn't it?

Check out Schnee-Morehead stuff sometimes if you're into higher quality products.
I'm about to get a case of their stuff for gluing aluminum plate to steel and aluminum.
The seam sealer works in places where nothing else does.
It's designed to go into metal seams, like the ends on crushed pipe.
Just try that with most sealers.

[EspressoDude]

yes primer layer is thicker, but it is the etch that is underneath that is important. the guy is painting a dome to put in the desert, not a Harley.

[gyre]

I think in any case, you should only sand enough to allow grip on the surface of the paint you are attaching to.
Presuming another layer of paint is going on anyway.

[Bob]

Just rough it up a little w/ a Scotchbrite pad and use the cheapest gray primer & paint you can find... try the auto parts stores. Leave the ends gray.

The conduit is already rusting on the inside, nothing you can do about that except store it in a dry place.